There are known several techniques for enriching uranium or, more accurately, producing enriched uranium, i.e. producing a uranium composition having a high concentration of the fissionable isotope of uranium.
Conventional techniques include the gas diffusion system, the centrifuge system and the separating nozzle system, all of which effect a concentration of the heavier and more fissionable isotope to bring about uranium enrichment. Uranium is generally converted into a gas and, as the gaseous compound, is subjected to the separating process.
The present invention is primarily concerned with improvements in the separating nozzle approach to uranium enrichment.
Such a separation-nozzle system may be of the type described in U.S. Pat. Nos. 3,668,080, 3,708,964, 2,951,554, 3,362,131, 3,877,892 and the patents and other references of record therein and of the same class.
The separating nozzles themselves are, for example, described in U.S. Pat. No. 3,668,080 and the units, hereinafter referred to as separating-nozzle units, can be of the type described in U.S. Pat. No. 3,708,964.
As is known in connection with separating nozzle techniques, the gaseous uranium (a uranium compound in a gaseous state) is subjected to compression subsequent cooling and passage through separating-element assemblies in which the enrichment takes place.
Thus, a typical apparatus for separating nozzle enrichment of uranium or isotope separation, comprises the separating-element assembly, an associated cooler, a respective compressor and the gas ducts for supplying the gas to the resulting unit and for delivering the gas of one unit to another unit or assembly. The units of course are connected in a cascade, generally known as a separating cascade.
While it is not uncommon to provide each unit (assembly of compressor, cooler, separator and ducts) as an integrated structure, it nevertheless is the practice to provide a multiplicity of such structures in spaced-apart relationship to constitute the separating cascade. Thus, each structure of the cascade must be connected to a preceding and successive structure by additional gas lines.
The disadvantages of such systems are numerous:
Firstly, the overall assembly, comprising a number of such structural units, occupies considerable space and requires more maintenance and higher capital cost than is desirable.
Secondly, the system needs long supply lines for the gases, for the cooling water and for the electrical power.
Thirdly, the number of individual units is considerable and separate monitoring and measuring devices must be provided for each of them, thereby creating high instrumentation and monitoring costs.
Finally, the cost of setting up and transporting the numerous individual units is considerable.
From a technological point of view, moreover, it is difficult to maintain the necessary high vacuum tightness of the numerous units, connecting fittings and the like of the cascade described above, particularly since each of the units generally has a large number of weld seams which must be prepared carefully and subjected to expensive testing procedures.
Taking all of the above-mentioned disadvantages into consideration, therefore, it will be apparent that the establishment of an installation with a separating cascade as described involves considerable capital cost, while the operation of the separating cascade involves considerable maintenance, repair and replacement costs and hence the technological advantage of the separating nozzle system may be outweighed by the unit cost for enriching the uranium. Thus, while theoretically the separating nozzle system is strongly competitive with other uranium enrichment systems, especially the gas diffusion process and the ultracentrfuge process, the disadvantages enumerated above have prevented widespread acceptance of this technique.